As technology advances in the electronics industry, mobile phones and portable devices have become popular in our daily life. Mobile phones are usually equipped with flat panel displays to display information. Among various types of flat panel displays, liquid crystal display (LCD) is the most mature technology and is also most popularized. Because a liquid crystal panel does not emit light by itself, a backlight unit is generally disposed below the liquid crystal display panel to act as a light source.
By applying different voltage levels to a liquid crystal, the liquid crystal can twist at varying degrees to change the amount of light passing through the liquid crystal. It takes certain time for the liquid crystal to change state, often referred as the response time of the liquid crystal. A ghost image may appear on the display panel when the liquid crystal is changing state and the backlight is turned on at the same time. A backlight blinking technique has been proposed to deal with the ghost image problem. The time duration that the backlight unit is turned on (referred as on-time in the following description) is shortened to reduce the overlapping between the backlight on-time and the liquid crystal transition time. However, the reduced backlight on-time decreases the image brightness on the display panel, which may cause visual discomfort to the user. Therefore, it is an important subject in the industry to design a brightness compensation method and circuit for the display device utilizing the backlight unit.